1. Technical Field
The invention relates generally to an improved bushing for a vehicle suspension system. More particularly, the invention relates to an improved bushing that provides different compliances in response to different loading conditions with the bushing being relatively simple to install. Specifically, the invention relates to a split bushing that provides a compliance in the horizontal direction that is different than the compliance in the vertical direction and that provides rotational and longitudinal support for a suspension beam and that allows for expedited installation with conventional hand tools.
2. Background Information
The trucking industry has witnessed a dramatic increase in the cost associated with the transportation of goods. High costs and increased competition mandate that over-the-road vehicles be utilized as efficiently as possible to minimize expense and maximize productivity. Thus, the industry is constantly in search of improvements that can then increase efficiency of trucks and/or reduce the cost of purchasing and operating trucks.
The bushings of truck suspension systems provide a coupling between the vehicle frame and the vehicle suspension beam to which the vehicle axle and wheels are connected. A typical trailing arm suspension system utilizes a suspension beam having a bushing seat at one end for holding a bushing therein. The bushing typically contains a bearing formed with a cylindrical hole, with the cylindrical hole carrying a hollow journal which holds a pin. The pin is attached to a hanger bracket on the vehicle frame and provides a rotational connection between the beam/bushing assembly and the vehicle frame. The suspension beam is connected at the opposite end to the vehicle axle which, in turn, supports the vehicle wheels.
Suspension system bushings are subjected to a wide variety of loads. Longitudinal loads result from acceleration and braking and are transmitted along the length of the beam to the bushing. Vertical loads result from a wheel on one side of the truck traversing an obstruction that the corresponding wheel on the other side of the truck does not traverse, such as when one side of the truck traverses a curb. Such differential loading of an axle causing a torque acting about a central axis of the beam to be transmitted along the length of the beam and onto the bushing. Rotational forces result from compression of the suspension system due to vehicle loading and unloading and due to the vehicle traversing obstructions in the road surface and are transmitted from the wheels to the bushing by rotation of the beam about the pin. Lateral loads result from turning of the vehicle and are transmitted along the beam and against the hanger bracket in a direction parallel with the pin. Such loading phenomena differ significantly from each other both as to magnitude and duration.
Bushings are often manufactured of materials having elastomeric properties whereby the bushings act in conjunction with springs and shock absorbers to provide an additional level of isolation between the vehicle frame and the vehicle wheels. Since the magnitudes and durations of the aforementioned loading forces and torques differ considerably, it is often desirable to design a bushing to provide multiple compliances whereby the bushing reacts differently to the various loading phenomena. For instance, a bushing may possess a first compliance to respond to a given set of forces as well as a lower compliance along a different axis to respond to higher forces occurring along that axis. Moreover, it is often desirable to provide a lateral bushing member between the bushing seat of the suspension beam and the hanger bracket to alleviate bearing stresses therebetween caused by lateral loading.
Such loading is typical of trailing arm suspension and is well understood in the relevant art. Moreover, bushings having different compliances responsive thereto are similarly known and understood in the relevant art. Various bushings, combined with washer-type lateral bushings, all of which are known in the art, have been employed in various combinations to counteract the effect of such forces with various degrees of success. Such bushing have often been difficult to install and have required specialized tools such as high-tonnage presses. Moreover, assembly of suspension beams in conjunction with washer-type lateral bushing members is tedious and difficult due to the multiplicity of components. Moreover, bushings responsive to the aforementioned loading phenomena have typically been costly, difficult to install, and of a limited useful life. Thus, the need exists for a bushing providing varying responses to the multiple loading phenomena experienced by a vehicle suspension, that is inexpensive, easy to install, and has an economical service life.
In view of the foregoing, an objective of the invention includes providing a bushing that provides a compliance in response to longitudinal loading of a suspension system caused by acceleration and braking of a vehicle.
Another objective of the invention is to provide a bushing that provides a compliance in response to vertical loading of a suspension system caused by the wheels of an axle traversing dissimilar obstructions in the roadway.
Another objective of the invention is to provide a bushing that provides a compliance in response to rotational loading resulting from compression of a vehicle suspension system.
Another objective of the invention is to provide a bushing that provides a compliance in response to lateral loading between a suspension beam and a hanger bracket acting in a direction parallel to the length of an axle pin and resulting from turning of the vehicle.
Another objective of the invention is to provide a bushing that provides multiple compliances for response to multiple loading configurations.
Another objective of the invention is to provide a bushing that provides a compliance for responding to vertical loading that is different than the compliance provided for responding to longitudinal loading.
Another objective of the invention is to provide a bushing that can be installed with conventional hand tools.
Another objective of the invention is to provide a bushing that is split into two halves.
Another objective of the invention is to provide a bushing having flanges formed integrally therewith at the outer ends thereof for reaction to lateral loading resulting from turning of the vehicle.
Another objective of the invention is to provide a bushing that reacts to vertical, longitudinal, rotational, and lateral loading modes.
Another objective of the invention is to provide a split bushing that responds to various combinations of vertical, longitudinal, rotational, and lateral loading.
Another objective of the invention is to provide a bushing that is inexpensive to manufacture.
These and other objectives and advantages of the invention are obtained from the improved bushing, the general nature of which can be stated as including a pair of bearings, each of the bearings having a hole therein, each of the bearings having an outer surface, an outer end, and an inner end, and each of the bearings having a radial compliance that varies about its circumference.